[Gambas-user] Val()

[Benoît Minisini]

Le 27/05/2021 à 15:58, John Anderson a écrit :
> On 5/26/2021 11:39 PM, CD wrote:
>> Hello,
>>
>> why Val("&FFFF") = -1
>> and
>> why Val("&FFFFFFFF") = -1
>>
>> is it normal?
>>
>> attached a TestVal project
>> Regards
>>
>>
>>
> 
> <APOLOGIES - CORRECTIONS ADDED>
> 
> Yes, that is correct: Val() returns a numeric value evaluated as the 
> -shortest-  integer type.  You have specified Short (2 bytes) in first 
> case, and a Long Integer (4 bytes) in the second case.  In both cases 
> the highest order bit of the variable is 1, hence both cases evaluate to 
> a value -1.
> 
> You can also do Val("&0000FFFF")  = 65535 ' The string dictates a Long 
> Integer
> 
> Or Val("&0FFFF")  = 65535  ' This string is considered a Long Integer also
> 
> Or Val("&HFFFF")  = -1  ' This string as a more formal designation for 
> Hex (Like VB)
> 
> Or Val("&x1111111111111111")  = -1   ' Binary string tells Gambas this 
> is a 2-Byte Short (similar to VB behaviour)
> 
> Or Val("&x11111111")  = 255   ' Binary string tells Gambas this is a 
> Byte (Like VB) - unsigned value - I haven't tested this extensively, 
> could also be considering this as Short
> 
> The documentation here is incorrect I think - it has left out the part 
> about "Short" (and maybe Byte) type evaluations being returned if 
> possible - I think that's where the confusion started:
> 
> https://gambaswiki.org/wiki/lang/val
> 
> -John
> 
> 
> 
> ----[ http://gambaswiki.org/wiki/doc/netiquette ]----
> 

I don't see where the documentation of Val() is incorrect, it does not 
talk about the difference between "&HFFFF" and "&HFFFF&", which is a VB 
horror introduced in Gambas to help old VB users.

The rule is the following:

If the number starts with "&" or "&H" (hexdecimal), "&X" or "%" 
(binary), and if the number -does not- ends with "&" or "U", then there 
is an automatic sign extension.

This automatic sign extension is done only if the number of digits 
equals a multiple of 16-bits integer (i.e. 4 or 8 digits in hexadecimal, 
16 or 32 digits in binary).

So be careful with that horror!

-- 
Benoît Minisini